Awesome thanks, yea I am not replacing rough for spec, but I have been spending time playing with its value, to see if it looks more accurate.
As I know its heavily based on your lighting and environment setup, but I have a hard time getting my materials to look like they do in substance. I seem to get the best result when I use t he pbr metal rough export preset than I do with the UE4 packed preset.
The only thing that really comes out all to lunch thats WAY!!! off from substance viewports are the opacity channels.
So I have been just making all my opacity stuff its own material and not painting them at all, just using unreals vector nodes to control my look, which is working out fine, as long as I dont want to included grunge or scratched details.
It seems like quality opacity in unreal is very advanced user, and sucks substance cannot export out opacity in a plug and play manner, even when I used designer and made a SBSAR, the opacity was super wrong.